Keystone Press

Hours after a bomb placed by Col. Claus von Stauffenberg failed to kill Adolf Hitler in 1944, Hitler showed Benito Mussolini, left, its damage. Lieutenant von Kleist’s role was to support a coup.

His death was reported by news outlets in Germany.

Like many Germans involved in efforts to kill Hitler, Mr. von Kleist was a soldier — a lieutenant in the German Army — but his family had long been active in the German resistance. In January 1944, he was 22 and recuperating in Berlin from wounds he suffered in combat when he was approached by Col. Claus von Stauffenberg to join an assassination plot.

At the time, Lieutenant von Kleist led a unit that was scheduled to meet with Hitler to show him new Army uniforms. Colonel von Stauffenberg asked Lieutenant von Kleist to take along hidden explosives, which he would then detonate at the meeting.

“I found it a very difficult decision, I must say,” Mr. von Kleist recalled in an interview for a 1992 documentary,“The Restless Conscience.”

He asked for a day to decide, and he traveled home from Berlin to talk with his father, Ewald von Kleist-Schmenzin. His father had been arrested many times for resistance activity.

“The next morning, my father said, ‘Why are you here again?’ “ Mr. von Kleist recalled. “I said, ‘Well, I have difficult decisions I have to make.’ He said, ‘What is it?’ And I told him. And he said at once, ‘Yes, of course you have to do it,’ and I said, ‘Yes, but I have to blow up with the colonel.’

“He got up from his chair, went to the window, looked out of the window for a moment, and then he turned and said: ‘Yes, you have to do that. A man who doesn’t take such a chance will never be happy again in his life.’ ”

Lieutenant von Kleist agreed to go through with the plan, but Hitler canceled at the last moment — he frequently changed his schedule late in the war — and Colonel von Stauffenberg and others began devising a new plan.

In July 1944, as other conspirators in the plot were being discovered and arrested, Colonel von Stauffenberg, whose Army role gave him access to top leaders, decided to leave a bomb under a table during a meeting of Hitler and his aides at Wolf’s Lair, his field headquarters in East Prussia. Lieutenant von Kleist was among several conspirators whose job was to wait in Berlin to be ready to stage a coup once Hitler’s death was confirmed.

Mr. von Kleist recalled the waiting that day as “a fantastic atmosphere when history is bending on the edge of a knife.”

When the bombing took place, on July 20, four people were killed, but Hitler was only slightly injured. The conspiracy was quickly discovered, and Colonel von Stauffenberg was among those who were arrested and shot to death late that night. Nazis eventually killed more than 5,000 people associated with or supportive of those involved in the plot. Mr. von Kleist’s father was arrested July 21 and killed by the Nazis in Plötzensee Prison in April 1945.

Mr. von Kleist was taken for questioning at the German Gestapo’s headquarters on the day of the bombing.

“I thought of the lines from the Divine Comedy: ‘Abandon hope, all ye who enter here,’ ” he said in a 2004 interview with The National Post of Canada.

Yet while he served time in prison with other conspirators, charges against him were eventually dropped, for reasons that were not immediately clear. He was assigned to combat duty on the front lines.

Mr. von Kleist told The National Post that he had benefited from the fact that conspirators who were being tortured did not disclose his involvement.

“Of course it helped me,” he said. “Some talked, and as a result some people were unnecessarily sent to the gallows.”

Ewald-Heinrich von Kleist was born on July 10, 1922, in the province of Pomerania, in what was then Prussia. His family had aristocratic roots, and his father had opposed Hitler even before he took control of Germany. In 1938, with Hitler well in charge, he traveled to England to try to convince the British that their support could help German military leaders overthrow Hitler.

After World War II, Mr. von Kleist became a book publisher. In 1962 he established an annual forum on security and defense issues in the West that has since expanded in scope to cover other regions. It is now called the Munich Security Conference; Vice President Joseph R. Biden Jr. spoke at the event in February.

Mr. von Kleist gave few interviews about his role in the plot. For a long time, attitudes in Germany about the effort were complex. Some people initially regarded it as treason — a development Colonel von Stauffenberg anticipated in his writings — but as decades passed more people embraced the plot, and for many years Germany’s leaders have been holding memorial services on July 20, sometimes accompanied by Mr. von Kleist.

Mr. Von Kleist appeared in several documentaries about the plot, but he was neither involved in nor portrayed in “Valkyrie,” the 2008 film about the plot starring Tom Cruise.